Each weekday until the Minnesota Vikings report to training camp on July 29, 1500ESPN.com's Tom Pelissero breaks down the roster at another position, based on offseason practice observations and conversations with coaches, scouts and personnel people around the NFL. Day 7: Linebackers.

Perhaps the biggest unknown on the Vikings roster is the health of E.J. Henderson (6-foot-1, 245 pounds), who sustained a gruesome fractured femur in December. Henderson proclaimed last month he'll be ready for camp and participated in individual drills in minicamp. But it remains to be seen how soon he's ready to take on a full workload and whether he can be the same player at age 30, less than a year after surgery and with a titanium rod in his leg. Scouts differ somewhat on the potential of Brinkley (6-1, 252) -- one felt he showed promise against the run for a rookie fifth-round pick, while another said he's "just a guy" and a third said the drop-off from Henderson last season was "enormous" -- but there's no question Henderson, when healthy, is superior in all phases and has experience on his side.

Greenway (6-2, 242) is an ascending, active player who led the team last season with 127 tackles (88 solo) and triggered an escalator that more than doubled his base salary this season to $3.17 million. Since losing his 2006 rookie season to a torn ACL, Greenway hasn't missed a game while remaining highly productive (407 tackles, five interceptions, six forced fumbles) and is playing for a big contract at age 27. Like Greenway, Leber (6-3, 244) can become a free agent after the season, and though he's no longer ascending at age 31, he still runs well and is an option in subpackages. His 70 tackles last season were his fewest since 2006.

Erin Henderson (6-3, 244) took a step forward in the offseason and worked with the first-team defense while Greenway sat out minicamp for undisclosed reasons. He figures as the top backup option outside, although Triplett (6-3, 247) -- the former Gopher drafted in the fifth round (167th overall) -- probably will get a long look there, too, even though he played inside in college. Farwell (6-0, 235), a Pro Bowl pick last season, and Onatolu (6-2, 225) tied for the team lead in special-teams tackles (24) but don't factor on defense. If Triplett makes the team, there may be room for only one of them. Leman (6-2, 240) was on the roster for five weeks last season but never was active.

Best battle

Depending on E.J. Henderson's progress, the Vikings will have to decide how to divide the work in base and nickel defense. And if they want to get Brinkley action, they have to do so in the base defense, because he lacks the lateral mobility and instincts at this stage to perform adequately in pass coverage. Given Henderson's injury, Leber and Greenway have to be the favorites for nickel duties entering camp. But there's really no telling how things will shake out until the preseason unfolds.

"He has inside run-stop ability. He can play downhill. He gives them size and strength as a potential downhill player. Probably equal to or less than in terms of the range of an E.J. Henderson. I think E.J. Henderson is going to be more of an initially instinctive player than what Brinkley brings to the table. But on first and second down, between the tackles, I don't see maybe a significant drop-off in that regard. Maybe a little concerned in terms of the know-how, the moxie, the awareness to the direct competitors in his division, the experience factor. You're going to want better for third down in your nickel and dime packages, but they have other linebackers that can come in and do those positions."

Outlook

With Henderson at full speed, scouts say, this is an active group that deserves more credit than it sometimes get for playing the run as well as dropping and making plays in space. It's hard to overstate the impact of his recovery on the fortunes of the entire defense. The starters are solid, but Brinkley remains unproven and depth outside is shaky as well.